Quote Originally Posted by Kraco
He said he was a new member. Perhaps he simply wasn't told yet. Maybe they first wanted to see he's in Akatsuki to stay, or more likely the big boss just hadn't bothered to tell before now. They are villains, after all.
I was meaning why Hidan wanted to join Akatsuki in the first place if he didn't know about the ultimate motive of Akatsuki to begin with. As villians, I wouldn't have expected them to simply "use each other" without exactly knowing what for.